Millions of HIV-1/AIDS patients suffer chronic pain. Morphine is a common analgesic for pain relief in these patients. Ironically, clinical data indicat that repeated morphine treatment leads a heightened chronic pain state. This problem is of great clinical importance since it suggests that HIV-1 patients receiving morphine to relieve pain may actually develop more pain as a result of treatment. Thus, there is a compelling need to understand how chronic morphine use causes this condition in HIV-1 patients. Using a mouse model that develops extensive abnormalities similar to the pain-related pathologies in HIV-1 human patients, we observed that chronic morphine administration potentiates HIV-1 gp120 (i.t.)-induced pain. Concomitantly, we found that chronic use of morphine also dramatically enhances gp120 (i.t.)-induced astrocyte activation in the spinal cord dorsal horn (SDH), the first pain processing center in the CNS. Our recent work suggests a key role of astrocyte activation in pain pathogenesis in HIV-1 patients. Hence, the morphine-enhanced astrocyte activation may provide an important cellular basis for morphine to potentiate HIV-related pain. The goal of this project is to understand the mechanism and consequences of the gp120-morphine interplay in astrocyte activation in the SDH. Our preliminary data show that chronic administration of gp120 and morphine cooperatively up-regulate Wnt5a, a secreted signaling protein that activates astrocytes but not microglia in the SDH. Based on ample preliminary data, we hypothesize that gp120 and morphine synergistically activate astrocytes by stimulating Wnt5a signaling and that the activated astrocytes enhance gp120-induced hyperalgesia by promoting cytokine signaling. This hypothesis will be tested in the proposed project under three specific aims. In Aim 1, we will identify the molecular pathways through which the gp120-morphine interaction stimulates astrocyte activation in the SDH. In Aim 2, we will establish the role of the mitochondria-inflammasome axis in control of cytokine signaling in astrocytes activated by gp120 and morphine. Finally in Aim 3, we will determine the contribution of astrocyte activation to the morphine potentiation of gp120-induced hyperalgesia. Results from this study will significantly improve our understanding of the mechanism by which the interplay of gp120 and morphine activates astrocytes in the SDH. The results will also help us understand how chronic morphine use enhances HIV-associated pain. The research has significant potential for the development of novel approaches to prevent the morphine-potentiation of hyperalgesia in HIV-1 patients.